Process for diffusion



June 11, 1935. J, BE 2,004,184

PROCESS FOR DIFFUSION Filed Feb. 9, 1931 2 Sheets-Sheet 2 WfW PatentedJune 11, 1935 UNITED STATES PATENT OFFICE Tirlemoutoise, Socit Anonyme,

Tirlemont, Belgium, a corporation Application February 9, 1931, SerialNo. 514,515 In Belgium February 11, 1930 1 Claim.

This invention pertains generally to the extraction of soluble matterfrom vegetable matter and particularly to such extraction by means ofdiffusion.

Although the invention will be described in connection with theextraction of sugar from beets, it is understood that it is applicablein many other ways.

The practice of extracting sugar from beets by means of diffusionembodies the fundamental principle of passing liquid of increasing sugarconcentration through beet slices of decreasing degrees of exhaustion.The results obtained will, of course, vary with the nature of thedevices used for applying the fundamental principle.

All prior devices, as far as applicant is aware, apply this fundamentalprinciple of diffusion imperfectly for the following reason: they areunable to prevent a more or less pronounced mixing of sugar liquors ofdifferent densities within the diffusers when the continuous column ofliquid is displaced, and a more or less pronounced mixing of slices indifferent stages of exhaustion when they are displaced.

Although kilograms of beets exhausted by these devices should result in,for instance, approximately 87 to 88 liters of relatively concentratedsugar liquor, or in other words approximately 95 kilograms of sugarliquor, and only a relatively small loss in extraction, these priordevices actually produce from to liters of relatively dilute sugarliquor and the loss in extraction varies between 0.30 to 0.50 kilogramsof beets.

Also, a quantity of water, equal to that employed for the extraction ofthe juice itself, is required for emptying the diffusers, so that anenormous amount of water is used in comparison with the weight of thebeets treated.

Even though the highestdegree of care is exercised in slicing the beetsand in the operation of these prior devices, it is practicallyimpossible to reduce the dilution of the final sugar liquor and todiminish the losses in extraction. In an effort to overcome thesedisadvantages it would seem logical to attempt to increase the number ofindividual diffusers in one series of difiusers. Practical difficulties,however, limit the number of individual diffusers that can beincorporated into one series in view of the increased resistance to fiowresulting from the addition of each diffuser. There is a practical limitin the water pressure which can be used at one end of a series ofdiffusers to cause the continuous column of sugar liquor of graduallyincreasing density to flow progressively from one diffuser to the nextin the series and to effect mashing and draining of the final diffuser.In practice the number of diffusers used varies between 10 to 16. It ispractically impossible to combine more than 16 diffusers in one seriesinasmuch as the resistance to flow caused by the total column of slices(the total column being calculated by adding the effective heights ofthe diffusers in the series) is such that if more than 16 diffusers wereplaced in one series the water pressure necessary to cause a flow wouldbe excessive. The necessity of maintaining tight joints about thecharging and discharging doors of each diffuser, and particularly thedanger of creating paths of lesser resistance through the slices thusleaving a large quantity of slices densely impacted and unpermeated by afiow of liquor, places a more or less definite, practical limit upon thewater pressure which can be employed. A very high pressure might evencause the slices to become so impacted as to prevent circulation ofliquor altogether. As a result of the foregoing, sugar manufacturershave generally adopted an upper limit of hydrostatic pressure ofapproximately 118 feet.

The above disadvantages are overcome in the present invention. Thedilution of the final sugar liquor, as well as the extraction losses, is30 reduced and the slices are exhausted more regularly. This results ina substantial reduction in the quantity of water required for theextraction of the sugar.

The invention comprises splitting up the liquor 35 column into a numberof parts, each having its own means for causing a flow of sugar liquor.This permits the use of an indefinite number of diffusers in a singlediffusion battery and prevents the mixture of liquors of differentdensities, 40 thereby considerably reducing the dilution of the liquorand consequently reducing the quantity of water necessary for effectingexhaustion of the slices.

In the accompanying drawings wherein like reference characters areappended to like parts in the various figures,

Figures 1, 2, 3 and 4 illustrate schematically diffusion batteriesaccording to the invention.

Figure 5 is a longitudinal section of a device 50 adapted for carryingout the invention.

Figure 6 is a transverse section of the device shown in Figure 5.

Referring to Figure 1, at III, II, l2, l3, l4 and I5 is shown a seriesof diffusers comprising a dif- 55 fusion battery. These diifusers aresix in numa is employed.

her, merely for illustrative purposes, and may be of any number withoutlimit. For the purpose of illustration the liquor will be considered aspassing from left to right from one diffuser to the next. Each cyclewill, of course; eliminate one diffuser with exhausted slices at theleft and will add one diffuser with fresh slices at the right. Theactual position of each diffuser with respect to the other, however, mayfollow the customary practice in this respect when a continuous columnThe liquor, therefore, will pass through diffuser ID to diffuser H, fromdiffuser H to diffuser I2, from diffuser l2 to diffuser l3, fromdiffuser l3 to diffuser M, from diffuser M to diffuser I5, etc.

Below each diffuser H) to l5 inclusive is shown a receptacle 20 to 25inclusive respectively. The liquor from each diffuser is drawn off intoits corresponding receptacle, the slices being drained of all liquorexcept that which adheres thereto and is contained therein.

The next step comprises draining the receptacles into the diffusers,each receptacle being drained into the diffuser next higher in theseries to its respective diffuser. The diffuser into which eachreceptacle is drained is shown diagrammatically in Figure 2. At the endof this operation the liquor of each diffuser will have proceeded firstinto its respective receptacle and then into the diffuser next higher inthe series. This progression of the liquor is accomplished without anymixture of the liquors of the diffusers and without the use of anyadditional pressure.

The use of the receptacles 20 to 25 inclusive is, of course, merely oneway of carrying out the invention, and the series of diffusers in adiffusion battery may be divided, for instance, into subseries, onesub-series taking the place of the receptacles 20 to 25 inclusive. Anarrangement of this character is shown in Figure 3 wherein the evennumbered diffusers comprise sub-series A and the odd numbered diffuserscomprise subseries B. Let us assume that the diffusers of subseries Acontain liquor and slices and that the diffusers of sub-series B containslices only.

The first step comprises passing the liquors from diffusers A intodiffusers B, that is from l0- into il from l2 into 13*, from [4 into I5from I6 into H, from [8 into [9 from 20 into 2 l etc., the progressionof the liquors from one diffuser to the next higher in the series beingshown by vertical arrows in Figure 3.

The second step comprises passing the liquors from the diffusers ofsub-series B into the diffusers of sub-series A, the liquor of eachdiffuser likewise passing to the difiuser next higher in the series. Theprogression of the liquors of each diffuser is shown by the inclinedarrows in Figure 3.

These operations are, of course, identical with those set forth inconnection with Figures 1 and 2 and produce the same results without amixture of liquors or the necessity of additional pressure.

The advantages of the invention are quite apparent:'

The liquor is no longer forced through the diffusers and, it bathes theslices of each diffuser successively, constantly increasing in sugarcontent. The use of pressure to cause a flow may be dispensed with andthe number of diffusers employed may be increased almost indefinitely.The dilution of the final liquor as well as the loss of sugar in theexhausted slices may be reduced as desired. The loss constituted by washwater and amounting to one-fourth to one-third of the total losses iseliminated. The simple bathing of the slices being substituted for theforced circu lation, the points of bad exhaustion of the slices, knownas the nests, disappear, whereby these losses, formerly indeterminate,are eliminated. The elimination of the residuary wash water materiallyreduces the quantity of water required.

With the new process, since the chip fragments do not hinder thecirculation, there is no objection to the pressure water of the pulpreturning again into the diffusion process, and this diminishes by onehalf the loss of sugar in the pulp.

A further advantage consists in the fact that the diffusers and otherreceptacles are always subject to inspection without difficulty. Thismakes it possible, for instance, to immediately check and prevent anyfermentation which might occur due to spoiled or poorly washed beets ordue to contaminated water.

In practicing the invention the quality of the liquor may be maintainedat a high standard and the tops or foam does not exist. The time duringwhich the slices are not covered with liquor is not lost to thediffusion inasmuch as the sugar liquor of the inner cells continuesduring this time to diffuse towards the film of juice which stilladheres to the outside of each slice. The diffusion also continuesinside of the slice itself from the center part which is less exhaustedtoward the peripheral portion.

The invention may be carried out in practice in various ways:

1) All of the diffusers may comprise covered containers provided withmeans for admitting air under pressure above atmospheric and with meansfor admitting air at atmospheric pressure. The passage of the liquorfrom the diffusers of sub-series A toward those of sub-series B wouldthen take place by admitting air under pressure into the former whilethe latter are open to the atmosphere. The passage of liquor from thediffusers of sub-series B toward those of sub-series A is likewiseaccomplished by subjecting the former to air under pressure while thelatter communicate with the atmosphere.

Since all of the operations are carried out from sub-series A towardsub-series B, or vice versa, it is possible to combine the opening andclosing of the air valves and the liquor valves of each sub-series so asto provide for simultaneous operation.

The operations for mashing and withdrawing the liquor from the diffusercontaining the fresh slices are very simple and well understood and nofurther explanation relative to this step is required.

It can be readily seen that diffusion batteries in present day use maybe readily adapted to the practice of the invention without unduemodification.

(2) Another method for carrying out the invention comprises making bothsub-series of diffusers movable. In the first step sub-series A, forinstance, may be placed above sub-series B so that the liquor may flowfrom the former toward the latter, and in the second step sub-series Bis placed above sub-series A for a like purpose. While this methodnecessitates movement of the diffusers it eliminates the necessity forcompressed air.

(3) The displacement of liquors may, of course, be effected by means ofpumps such as centrifugal pumps or other device.

(4) Another way of carrying out the invention is to leave the liquor inthe diffusers and move the slices from one diffuser to the next in theseries. Inasmuch as the liquor has been previously considered astravelling from a diffuser lower in the series to a diffuser higher inthe series it is to be pointed out that the slices would move from adiffuser higher in the series toward a diffuser next lower in the seriessince the travel of the slices is theoretically opposite to that of theflow of liquor. The operation consists in withdrawing the slices fromone diffuser and placing the same in the next diffuser lower in theseries. This operation for all of the diffusers may be madesimultaneously if desired. The slices, of course, travel from liquors ofhigher concentration, to liquors of lower concentration. An example ofthe necessary operations. is schematically illustrated in Figure 4 inwhich perforated baskets are illustrated as being adapted to be immersedin diffusers, said baskets conforming to the shape of the diffusers. Thediffusers are illustrated at 30 to inclusive and the baskets at toinclusive. It is, of course,

understood that the diffusers and baskets may be of any number.

The first step of the operation comprises withdrawing the perforatedbaskets 40 to 45 inclusive from the diffusers 30 to 35 inclusive. Thesecond step comprises inserting each basket into a diffuser next lowerin the series. Let us assume that basket 40 has been withdrawn fromdiffuser 30, basket 4| from diffuser 3|, basket 42 from diffuser 32,basket 43 from diffuser 33, basket 44 from diffuser 34, basket 45 fromdiffuser 35, etc. in the first step. In the second step, basket 40 isinserted in diffuser 3|, basket 4| in diffuser 32, basket 42 in diffuser33, basket 43 in diffuser 34, basket 44 in diffuser 35, basket 45 eitherinto the next diffuser or, if the slices in this basket are to beconsidered exhausted, the basket is merely emptied and the slices thenpass along and are taken care of in the usual way. The liquor indiffuser 30 which may have previously been used for mashing the freshslices in basket 40 constitutes final liquor. The diffuserstheoretically pass toward the left in the figure and the perforatedbaskets to the right. Diffusers with fresh water are added on at theright and diffusers with finished liquor removed at the left, andbaskets with fresh slices added at the left and baskets with exhaustedslices removed at the right.

Either manner of proceeding whether by displacement of the liquor or bydisplacement of the slices accomplishes the same results, to wit: anappreciably better degree of exhaustion of the slices than has beenobtainable by the ordinary methods and a final liquor of a much lesserdegree of dilution. The undetermined losses in diffusion are thuseliminated and the quantity of water necessary for carrying out theprocess is greatly reduced, not taking into consideration theelimination ofthe washwaters for removing the exhausted slices from thediffusers.

The invention may be carried out either continuously or otherwise and infact may be almost automatic.

Present day apparatus might be adapted for this purpose.

Such apparatus heretofore, however, has mixed the liquors of the variousstages of diffusion or the slices, or has mixed the liquors and theslices with the result that the exhaustion of the slices was incompleteand the amount of liquor drawn off too great and thereforeinsufficiently concentrated.

These devices, therefore, have never been adapted for carrying out thefundamental principle of this invention which is characterized by thecomplete segregation of the liquors of the various stages of diffusion.

Apparatus adapted for carrying out the invention continuously isillustrated in Figures 5 and 6.

At is shown a cylindrical casing having a helical shaped screw 5|arranged longitudinally therein and secured to the walls thereof. Thisscrew is horizontally arranged and may be very similar to an Archimedianscrew.

Should the cylindrical casing be filled with water to the levelrepresented by the dotted line CC so that it does not overflow the freeedges of the various turns of the screw, it can be seen that each fullturn of the screw will bound a compartment 52 and that each compartment52 is isolated from all of the others.

If the cylindrical casing is caused to rotate slowly about itshorizontal axis the level of liquid in each compartment will remainhorizontal and the liquid will be moved in a direction along the axis ofthe cylindrical casing depending upon the direction of rotation. Thisprogression of the liquid from one end to the other of the cylindricalcasing 50 takes place without any mixture of the liquid in onecompartment with that of another. At each complete revolution of thecylindrical casing 50 the liquid in each compartment advances one stepor a distance equal to the pitch of the screw, or, in other words, thewidthof one compartment. If the rotation is counter clockwise, as shownin Figure 6, the liquid will progress from right to left as seen inFigure 5.

Spaced perforated plates 53 are arranged between the turns of the screw5! as clearly shown in Figure 6. These plates being perforated will notinterfere with the movement of the liquid as previously described.inasmuch as the liquid passes through the perforations. However, whenthe compartments contain both liquor and slices the latter will be drawnup out of the liquid by the plates 53 upon rotation of the drum and willbe brought to substantially its highest point. During their travel theslices shed their liquor which flows back to its respective compartment.The slices will then fall vertically in a direction toward the lowerportion of the cylindrical casing. Considering the slices which at acertain mo-- ment occupy a particular compartment such as, for instance,52A, the time which will pass between this moment and the instant atwhich these slices, after being carried along by the rotation of thedrum, will fall downwardly will correspond approximately to one-half arevolution of the drum. During this time the liquid will advancelongitudinally a distance corresponding to one-half of the pitch of thescrew or one-half the width of a compartment. The slices therefore willfall in a manner such as to be divided between two compartments,one-half falling back into the compartment which they left and the otherhalf falling into the compartment just preceding. With this arrangementthe slices have no movement longitudinally of the casing 50 during thetime contemplated which begins at the emergence of the slices from theliquid and terminates after the fall of the latter.

In order that the movement of the slices will be contra to that of themovement of the liquor a longitudinally-extending fixed support 54 maybe arranged axially of casing 50 and a plurality of inclined plates 55arranged along the support 54. The inclination of the plates 55 is suchthat Cir they will advance slices falling thereon to the right, as seenin Figure 5, the distance of one-half the pitch of the screw. Theoperation of these plates is such that when the slices in falling strikethese plates the slices from any one compartment will be completelydeposited in the next compartment. The slices, therefore, progress fromleft to right from one compartment to the next without a mixing of theslices ofone compartment with those of another;

It can be seen that this device permits continuous diffusion, preventsundesirable mixtures, and takes the place of as many consecutivedifiusers as there are turns in the helical wall 5|. Mixtures areeliminated because the liquors of the various diffusers do not come intocontact at any time and the groups of slices travel through theapparatus without a mixture of the groups and at exactly the same speedthus exposing each group of slices to difiusion for the same period oftime.

The liquor and the slices progress simultaneously in oppositedirections. The feeding of the slices and the discharging of the pulp aswell as the feeding of water and the flowing off of liquor take place atopposite ends of the casing 50.

Heating may take place from either the outside or the inside of the drumor by any means known in the art.

It is also understood that calorisators or other heating means forrealizing the well known systems of Stefien or of Naudet relating to thescalding of the slices and the reheating of the juice may be combinedwith any ways for carrying out the invention described herein, ifdesired.

For the purpose of rotation, casing 50 is shown provided withcircumferential riding rings 56 which fit within grooves 51 in rollers58. Rollers 58 may be mounted and spaced as shown at 59 for the purposeof supporting'casing 50. It is,

of course, understood that any other structure may be used for thispurpose as well as for the other parts specifically described inconnectio with the description of Figures 5 and 6 withou departing fromthe spirit of the invention.

Although this invention has been described in connection with theextraction of sugar from beets it is in no way limited thereto but maybe applied to vegetable products in general, particularly thosecontaining extractable sucrose such as sugar cane and the like, as wellas to the treatment of chicory root, Jerusalem artichokes, dahlias orother roots or tubercles, for instance, for extracting inulin therefrom.Furthermore, the invention is not limited to the several modificationsdescribed herein, these being given merely by way of example, and it isunderstood that any device which would permit the realization of theabove described novel principle falls within the scope of thisinvention.

Having described my invention it is obvious that many modifications maybe made in the same within the scope of the claim without departing fromthe spirit thereof.

I claim:

The process of extracting sugar from beet slices the cell walls of whichhave been preserved intact except for surface ruptures occurring in theslicing operation, which comprises providing a confined column of Waterin successively segregated masses, simultaneously and continuouslymoving said segregated masses of water along a substantially horizontalpath; providing a mass of beet slices and simultaneously moving saidbeet slices in a similar column of segregated masses continuously and ina substantially coaxial sinuous path through said column of segregatedmasses of water in countercurrent relationship thereto at atmosphericpressure.

JULIEN BERGE.

